As shown in FIG. 1, a conventional liquid crystal display device comprises an opposite substrate 101 and an array substrate 102 which are bonded together by a sealant 103 to form a liquid crystal cell, and a liquid crystal 104 is filled in the liquid crystal cell. Spacers are generally formed on the opposite substrate 101 and are used for keeping a gap of the liquid crystal cell.
Generally, the spacers comprise a main spacer 106 and an auxiliary spacer 107. After the opposite substrate 101 and the array substrate 102 are bonded together, the main spacer 106 contact with a pad 105 provided on the array substrate 102. The auxiliary spacer 107 is used as a spare spacer, and assists the main spacer 106 to keep the gap of the liquid crystal cell when the liquid crystal display device is pressed by a strong force.
In a unit area, a contact density between the main spacer 106 and the array substrate 102 is a quite important parameter, particularly for an IPS (In Plane Switch) mode liquid crystal display device which is more sensitive to Mura defect (Mura defect is an image quality defect caused by uneven brightness). Too high or too low contact density will bring about negative impact on LC Margin (LC Margin is a liquid crystal amount range where the liquid crystal screen is free from gravity Mura at high temperature and free from bubbles at low temperature) and on image quality.
In the case that contact density between the spacers on the opposite substrate and the pads on the array substrate is too low, the support strength of the spacers is insufficient at high temperature so that the liquid crystal is gathered on the lower side of the liquid crystal screen under gravity and a gravity Mura occurs, as shown in FIG. 2. In the case that the contact density between the spacers and the pads is too high, the liquid crystal shrinks and liquid crystal volume is reduced at low temperature but the cell gap is not correspondingly reduced due to too high support strength of the spacers, so that bubbles appear on the corners of the liquid crystal screen, as shown in FIG. 3.